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The presence of massive galaxies at high $z$ as recently observed by JWST appears to contradict the current $\Lambda$CDM cosmology. Here we aim to alleviate this tension by incorporating uncertainties from three sources in counting…

Astrophysics of Galaxies · Physics 2025-04-08 Yangyao Chen , H. J. Mo , Kai Wang

The simple assumption of an instantaneous reionization of the Universe may bias estimates of cosmological parameters. In this paper a model-independent principal component method for the reionization history is applied to give constraints…

Cosmology and Nongalactic Astrophysics · Physics 2015-12-21 Wei-Ming Dai , Zong-Kuan Guo , Rong-Gen Cai

Cosmic Microwave Background temperature and polarization anisotropies from Planck have estimated a lower value of the optical depth to reionization ($\tau$) compared to WMAP. A significant period in the reionization history would then fall…

Cosmology and Nongalactic Astrophysics · Physics 2020-08-19 Dhiraj Kumar Hazra , Daniela Paoletti , Fabio Finelli , George F. Smoot

We present cosmological constraints from the combination of the full mission 9-year WMAP release and small-scale temperature data from the pre-Planck ACT and SPT generation of instruments. This is an update of the analysis presented in…

The $James \ Webb \ Space \ Telescope \ (JWST)$ recently reported a large population of UV luminous galaxies at high redshifts, $ z > 10$, as well as Lyman-$\alpha$ emitting (LAE) galaxies out to $z \sim 11$. We use the observed UV…

Cosmology and Nongalactic Astrophysics · Physics 2024-10-04 Hamsa Padmanabhan , Abraham Loeb

Interest in non-standard recombination scenarios has been spurred by recent cosmic microwave background (CMB) results from BOOMERANG and MAXIMA, which show an unexpectedly low second acoustic peak, resulting in a best-fit baryon density…

Astrophysics · Physics 2009-10-31 Steen Hannestad , Robert J. Scherrer

In this first of several application papers, we investigate the mechanics of reionization from stellar sources in high-z galaxies, the utility of various clumping factors on estimating the recombination time in the IGM, and the photon…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-17 Geoffrey C. So , Michael L. Norman , Daniel R. Reynolds , Robert P. Harkness

The cosmic microwave background provides an image of the Universe 0.4 million years after the big bang, when atomic hydrogen formed out of free electrons and protons. One of the primary goals of observational cosmology is to obtain…

Astrophysics · Physics 2007-11-27 Abraham Loeb

We compare model results from a semi-analytic (merger-tree based) framework for high-redshift (z ~ 5-20) galaxy formation against reionization indicators, including the Planck electron scattering optical depth and the ionizing photon…

Cosmology and Nongalactic Astrophysics · Physics 2017-02-22 Pratika Dayal , Tirthankar Roy Choudhury , Volker Bromm , Fabio Pacucci

The JWST early release data show unexpected high stellar mass densities of massive galaxies at $7<z<11$, a high star formation efficiency is probably needed to explain this. However, such a high star formation efficiency would greatly…

Cosmology and Nongalactic Astrophysics · Physics 2023-04-26 Yan Gong , Bin Yue , Ye Cao , Xuelei Chen

Recent JWST observations indicate that star formation at $z\!\sim\!4-6$ is more stochastic than previously assumed, with rms log-SFR scatter $\sim\!0.6$ dex at $M_h\!\sim\!10^{11}M_{\odot}$, growing toward smaller halos and time-correlated…

Astrophysics of Galaxies · Physics 2026-05-15 Ely D. Kovetz , Hovav Lazare , Sarah Libanore , Julian B. Muñoz , Eleonora Vanzan

Recent observations with JWST have identified several bright galaxy candidates at $z\gtrsim 10$, some of which appear unusually massive (up to $\sim 10^{11}\ \rm M_{\odot}$). Such early formation of massive galaxies is difficult to…

Cosmology and Nongalactic Astrophysics · Physics 2022-10-05 Boyuan Liu , Volker Bromm

The reionization of cosmic hydrogen marks a critical juncture in the history of structure formation in the universe. Here we present a new formulation of the standard reionization equation for the evolution of the volume-averaged HII…

Astrophysics of Galaxies · Physics 2017-12-13 Piero Madau

We forecast cosmological parameter constraints for a cosmic shear analysis of the Rubin Observatory Legacy Survey of Space and Time (LSST), defining an analysis framework that can accurately recover the $\Lambda$CDM model in the presence of…

Cosmology and Nongalactic Astrophysics · Physics 2026-03-03 N. C. Robertson , C. Heymans , J. Zuntz , P. Burger , C. D. Leonard , I. G. McCarthy , J. G. Paine , J. Salcido , N. Šarčević , M. Schaller , J. Schaye , M. P. van Daalen

The James Webb Space Telescope (JWST) is expected to observe galaxies at $z>10$ that are presently inaccessible. Here, we use a self-consistent empirical model, the UniverseMachine, to generate mock galaxy catalogues and lightcones over the…

The James Webb Space Telescope (JWST) is unveiling astounding results about the first few hundred million years of life of the Universe, delivering images of galaxies at very high redshifts. Here, we develop a UV luminosity function model…

Cosmology and Nongalactic Astrophysics · Physics 2024-09-17 Fabio Iocco , Luca Visinelli

Since the public release of Planck data, several attempts have been made to explain the observed small tensions with other data-sets, most of them involving an extension of the {\Lambda}CDM Model. We try here an alternative approach to the…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-18 Benjamin Audren

Planck data provide precise constraints on cosmological parameters when assuming the base $\Lambda$CDM model, including a $0.17\%$ measurement of the age of the Universe, $t_0=13.797 \pm 0.023\,{\rm Gyr}$. However, the persistence of the…

Cosmology and Nongalactic Astrophysics · Physics 2021-06-28 Michael Boylan-Kolchin , Daniel R. Weisz

The timeline of cosmic reionization remains uncertain despite sustained efforts to study how the ionizing output of early galaxies shaped the intergalactic medium (IGM). Using the semi-numerical code LIMFAST, we investigate the prospects…

Cosmology and Nongalactic Astrophysics · Physics 2025-01-22 Guochao Sun , Adam Lidz , Tzu-Ching Chang , Jordan Mirocha , Steven R. Furlanetto